1. Field of the Invention
The present invention relates to a power transmission apparatus.
2. Description of the Related Art
In a rear wheel side power transmission system of a four-wheel drive vehicle, such as a power transmission apparatus arranged between an input shaft in a side of a propeller shaft and an output shaft in a side of a rear differential gear which executes a torque transmission from the input shaft to the output shaft, for example, there is a structure described in Japanese Patent Application Laid-Open (JP-A) No. 10-329562.
A conventional power transmission apparatus has a sub-clutch apparatus connected to the input shaft, arranged between an electromagnet and an armature and operating according to a pressing motion applied by the armature attracted due to an excitation of the electromagnet so as to frictionally engage. A main clutch apparatus is arranged between the input shaft and the output shaft and is frictionally engaged by a pressing force, thereby executing a torque transmission between the input shaft and the output shaft. A cam apparatus converts a frictional engagement force of the sub-clutch apparatus into the pressing force for the main clutch apparatus.
In the prior art, the electromagnet is arranged on one side in an axial direction of the sub-clutch apparatus, and the main clutch apparatus is arranged on another side in the axial direction of the sub-clutch apparatus. Accordingly, the electromagnet, the sub-clutch apparatus and the main clutch apparatus are arranged in an axial direction of the power transmission apparatus, whereby the size in an axial direction is unfavorably increased.
An object of the present invention is to reduce the size in an axial direction of a power transmission apparatus having a sub-clutch apparatus, a main clutch apparatus and an electromagnet.
According to the present invention, there is disclosed a power transmission apparatus having a sub-clutch apparatus, a main clutch apparatus, and a cam apparatus, wherein a torque transmission is executed between an input shaft and an output shaft.
The sub-clutch apparatus is connected to the input shaft. The sub-clutch is arranged between an electromagnet and an armature and operates according to a pressing motion applied by the armature attracted due to an excitation of the electromagnet so as to frictionally engage.
The main clutch apparatus is arranged between the input shaft and the output shaft and frictionally engages due to a pressing force, thereby executing the torque transmission between the input shaft and the output shaft.
The cam apparatus converts a frictional engagement force of the sub-clutch apparatus into the pressing force for the main clutch apparatus.
The electromagnet is arranged in an inner diameter side of the main clutch apparatus.